Tuesday, October 23, 2012

The Mysteries of the Cuckoo. Pt. 1

I have been hooked by the BTO’s Cuckoo project and so I have
been catching-up with some of the Cuckoo related literature on my book-shelf. I
came across ‘The Cuckoo and Other Bird Mysteries' by Bernard Acworth. A book
which I expect I bought from a charity or second-hand book shop and then forgot
I owned. Excellent, I thought, a good
Cuckoo read. How wrong! It is a completely bonkers book by an unusual
author. Ignoring the first half of the book which deals with the ‘other bird
mysteries’ ( in which he proves that birds do not migrate – they get blown
away!) to concentrate on the latter half we find the following ‘facts’ about the
European Cuckoo. The Cuckoo’s unnatural practice of laying its eggs in the
nests of other species, which has made the term ‘a cuckoo in the nest’ a common
figure of speech makes the cuckoo the enemy of an ‘otherwise ideally moral bird
society’ and so it is ‘an abomination.’ Acworth
assures the reader that there is a ‘monogamous tradition of birds under wild
conditions’ but the Cuckoo breaks this tradition by being polyandrous due to
the fact that males outnumber females by six to one. As regards the fosterers,
early on we find that by accepting and brooding the innocent-looking Cuckoo’s
egg the mother of a legitimate brood will ‘hatch a domestic bombshell for
herself, her husband, and her family.’ Initially we are struck by Acworth’s
anthropomorphic language. Don’t be in any doubt that he means it. When he uses
terms like ‘husband’ that birds have ‘monogamous traditions’ and Cuckoo’s eggs
are ‘bombshells’ he believes these expressions to be completely accurate. He
continues by saying that the egg is phenomenally small for a bird of its size.
But stranger is its almost chameleon-like colouring, which frequently resembles
the eggs of its host. But the greatest Cuckoo mystery is’ how does the Cuckoo
so successfully and so secretly insinuate its startlingly small egg into the
nests, often the tiny and fragile nests, of the little dupes?’

Bottom: The Cuckoo from Willughby's Ornithologia libri tres of 1667

A list is then presented to the reader. It contains six
questions that constitute the main features of the Cuckoo problem. It is
interesting to ponder all of them but not as interesting as his answers.

1.How did the unnatural (!) parasitic habits
of the Cuckoo originate?

He does not have an answer. He does not
like any suggestion that the trait evolved over time in response to external
environmental factors, rather opting for something along the lines of ‘desire
or design on the part of the Cuckoos in the dim shadows of countless ages past.’

Plates from August Carl Edouard Baldamus's 1892 Life of European Cuckoos

2. How does the Cuckoo adjust the time of the insinuation of the egg into another bird's nest so as to ensure that it will be hatched at the right moment?Again he
has no answer but discusses the explanations prevalent at the time of writing. That
at the sight of a prospective foster-bird building, the Cuckoo’ conceives’ her
egg, and she is ready to lay in the chosen nest before the owner has commenced
to incubate. This is based on a process of watching and searching.
Alternatively the female Cuckoo knows when to lay by thieving one of the
fosterer’s eggs and testingit to see
whether it is fresh or partially incubated.

3. How does the Cuckoo contrive, as a general rule,
to match its eggs tolerably well, and sometimes perfectly, with the variously
coloured eggs of the different nests which house it?Acworth,
not surprisingly, treats this as a mystery still unsolved. He rejects any
answer based upon evolution or adaptation by natural selection as such answers
contradict his religious views. Coincidence is rejected. The theory that the
Cuckoo laid its egg on the ground then hawked it around until it found matching
eggs is rejected. That the Cuckoo wills a suitable colouring and marking is
also rejected. Acworth clearlyhad some
sense. The idea that the Cuckoo has
evolved the habit of depositing its egg in the nest of the same species of ‘fosterer’
as had fostered that particular Cuckoo and its forebears and consequently in
time the Cuckoo’s egg gradually changes to the colouring and marking of its
regular fosterer is also, unfortunately, rejected because fostering does not
affect physically the object fostered.

4.Why is the
Cuckoo’s egg unique in being generally, though not always, only a fraction of
the size to be expected of so large a bird, and why do Cuckoos’ eggs vary in
size? Answer: ‘No explanation of this size mystery has, so far as is known,
been put forward.’ The explanation afforded by the theory of evolution i.e. of adaptation
through selection is rejected because Cuckoos would never have survived in the
past as their eggs would have been the wrong size.

5.How does
the Cuckoo insinuate the egg into the small birds’ nests?Cuckoos are big, nests of fosterers tend to be
small. Often in tangled bush, on fragile reeds, in holes in banks or in and
down a tree trunk frequently inaccessible to a big bird. ‘Little wonder,
therefore, that ornithologists are perplexed about the method of egg deposition
by the cuckoo’. Possible solutions: The Cuckoo swallows its egg and spews it forcefully
into the nest – not taken seriously. The Cuckoo lays it in its chosen nest like
any other bird – but Cuckoos’ eggs have been taken from nests in holes to which
it would have been impossible for the Cuckoo to have obtained access. The
Cuckoo lays its egg on the ground then carries it in its beak to the
prospective nest where it places it – Acworth leans towards this even though
there is little to no evidence. The Cuckoo projects or squirts its egg into
nests – this will explain how eggs are found in some inaccessible nests.The Cuckoo uses a combination of all four
methods. Again Acworth ends this question by writing: ‘Little wonder, indeed,
that the method of egg deposition in inaccessible nests remains a problem hotly
disputed by ornithologists.’

6.Why should the sinister word ‘cuckold’ be
derived from the Cuckoo if the small female bird is a foster-mother? Bit of
a side issue this. The male Cuckoo is not, in fact, cuckolded – none of the
birds are. People subconsciously associate the secret life of the unfaithful
wife with the secret of the Cuckoo.Now
here’s interesting! Acworth suggests that if evolutionary theory be true it is
possible that the Cuckoo has evolved its ‘chuckle’ as a mocking response to
human beings lack of understanding of the birds’ secrets. Blimey!

Now here’s the rub. Acworth states that five of the six
problems given above would all be solved at a stroke if we accept his theory, the off-the-wall theory that Cuckoos are nearly all hybrids of pure male Cuckoos and female foster
birds! The correct moment of incubation, the varying number of eggs laid by a Cuckoo
in any season; the matching of the eggs in colour, marking and size and the
insinuation of eggs into inaccessible nests are all solved. And the little male
‘foster-father’ really would be a cuckold.

Elizabeth Gould or Edward Lear. Goulds Birds of Europe: The Common Cuckoo 1837

So there we have it there are lots and lots of Robin-Cuckoos
and Meadow Pipit-Cuckoos and Dunnock-Cuckoos out there. That will please the
splitters! This book was written in 1944 and the last 68 years has seen significant progress in our knowledge and understanding of the life of the Cuckoo. Anyone following the fortunes of the BTO's Cuckoos fitted with satellite tracking devices will be aware of how much new information we are getting even as I write. Acworth would have been dumbfounded and astonished. But I doubt if he would have changed his views. Follow the BTO Cuckoo tracking project here: http://www.bto.org/science/migration/tracking-studies/cuckoo-tracking